1. Field of the Invention
The present invention relates to drive assemblies for chain driven bicycles. Most state-of-the-art multi-speed bicycle drive systems seen on both mountain and road bicycles on the market today utilize a three piece crank assembly, supported through a bottom bracket, for conveying the physical motion of a rider through a chain, about a rear freewheel cassette, and through both front and rear derailleurs so that the bicycle will move. However, in order to shift the gears on these bicycles, the rider must be in the process of pedaling the bicycle. This is due to the fact that the chain must be moving across the front chain rings and the rear freewheel cassette as well as the rear or front derailleur, whichever is being used at that time to change gears. Because the rear freewheel cassette is constructed not to rotate, i.e. it disengages, when the rider is not powering the bicycle and/or is coasting on the bicycle, as is common when descending a hill, the rider is unable to change gear or shift at that time. The present invention eliminates this problem of not being able to shift when not pedaling by providing a drive assembly that may be incorporated into any multi-speed bicycle having a three piece crank assembly and a rear freewheel cassette. The present invention accomplishes this by "freewheeling" the front chain rings of the crank assembly about the crank axle and by locking the rear freewheel cassette to rotate with the rear wheel. Hence, as long as the bicycle is moving, the chain will be moving and therefore, the gears may be shifted.
2. Description of the Prior Art
The patent record shows that one-way clutches for "freewheeling" both the rear cassette and the front chain rings of a bicycle have been patented in the past. Friction plates for locking a rear freewheel cassette at the same rotational speed as the rear wheel of a bicycle, however, are not as clearly defined within the patent record.
U.S. Pats. Nos. 3,386,544 and 4,650,049 issued to Minoru Matsuda on Jun. 4, 1968, and Charles W. Stephens on Mar. 17, 1987, respectively, disclose coaster brake apparatus. Matsuda's coaster brake is an automatically disengaging ratcheting coaster brake that engages and stops the hub of the wheel when a connected pedal is pressurized and disengages when the pedal is neutral or when the wheel of the bicycle is moved in a reverse direction. The Stephens patent discloses a rear hub for a bicycle that is capable of functioning both as a coaster brake and as a freewheel. Neither of these rear wheel hub engaging brake and freewheel mechanisms are fully removable from the hub without making it impossible for the bicycle to operate nor do they create a 1:1 transfer of rotational motion from the wheel to the hub as is accomplished by the friction plate of the present invention.
U.S. Pats. Nos. 4,145,095, 4,154,123, 4,154,327, and 4,840,084 disclose a number of ratchet-type one-way clutches, or freewheel cassettes, having a number of different configurations relating to the hub itself as well as the positioning of ball bearings therewithin. These devices will are not capable in their patented configurations to adapt to an existing crank axle and freewheel the front chain ring with respect to the crank axle.
Crank assemblies having the ability to freewheel are disclosed in U.S. Pats. Nos. 3,492,883, 4,450,859, and 4,183,262, issued to Tetsuo Maeda, Takashi Segawa et al. and Takashi Segawa, respectively. Maeda's drive chain gear of a bicycle suggests that it is possible to freewheel a front chain ring in such a manner that pedaling is not required to shift the gears of the bicycle. However, Maeda's invention does not have means for holding the rear freewheel at the same rotational speed as the rear wheel of the bicycle, thus shifting without pedaling is not always possible, it is only possible under certain, not all, coasting speeds. Looking now at Segawa's patents, two freewheeling cranks are disclosed; the first is a three piece crank while the second is a more traditional one piece crank. Specifically, Segawa's three piece crank, having freewheeling capabilities, requires the installation of a new crank assembly and bottom bracket. In addition, the one-way clutch mechanism of the freewheeling crank assembly is attached to the crank axle itself, thus it and the chain rings attached thereto, are not a part of the crank arm and cannot be easily removed.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.